Energy Modeling Versus Reality

Modeling software can be very useful for helping you understand how a building works. As I’ve described in previous articles, you can calculate heating and cooling loads, HVAC air delivery requirements, and duct layouts. You can tweak construction assemblies to your heart’s content to see, at least in theory, how a building’s energy consumption changes. You can change orientation and glazing to estimate the impact of various passive-solar strategies. The combinations of variables are endless.
Underlying this process are usually complex algorithms based on research done by dozens of well-respected researchers from some of the most prestigious institutions in the world. The key question is, How well do these modeling programs reflect reality? After all, if we want to predict the effect of a change to a building, we have to know exactly how that change affects the building’s energy consumption. This question raises a variety of issues.
First, you have to decide how to measure reality. That’s usually done in some standardized
unit, such as kWh for electricity or thermsmfor natural gas. However, there may be other useful metrics—daylight penetration, occupant comfort, humidity levels, temperature changes, room-by-room ...